Television system



June 11, 1946. o. H. SCHADE I TELEVISION SYSTEM Filed Dec. 31; 1941 ATTORNEY Patented June 11, 1946 Otto H. Schade, West Caldwell, N.-J., asslgnor to Radio Corporation-of America, a corporation of Delaware Application December 31, 1941, Serial No. 425,088

'(c1. its-7.2)

11 Claims. 1

This invention relates to an improvement in television systems and more particularly to an improvement in systems for generating synchronizing signals and transmitting apparatus defiection voltages.

In present-day television systems the receiving apparatus are maintained in synchronous operation with the transmitting apparatus by means of transmitted horizontal and vertical synchronizing signals. These signals are normally transmitted along with the picture signals, the picture signals and the synchronizing signals being used to modulate a single radio frequency carrier wave. In order that the synchronizing signals may be interspersed with the picture signals, the picture signals are entirely eliminated during periods of synchronization and in lieu of the eliminated picture signals the desired vertical or horizontal synchronizing signals are transmitted. It is also conventional practice to transmit the synchronizing signals in such a direction that they are in the direction of black in the picture and extend further in that directionthan the blackest black (i. e., they are blacker-thanblaclr) so that when the composite series-is applied to a television receiving tube the syn chronizing signals will inherently cause blanking of the cathode ray beam in the receiving tube during return deflection intervals.

Various systems have been used for producing the desired blanking, synchronizing and deflection voltage variations that are necessary at the transmitter but in most instances such systems are rather complicated and involve a considerable number of tubes and circuit components. Furthermore, in some systems, considerable additional circuit arrangements have been included in order to transmit impulses of double horizontal deflection frequency immediately preceding, during, and immediately following the transmission of the vertical synchronizing impulse. Such transmission is generally known as slotted vertical synchronizing and although the use of such a synchronizing method has certain advantages it has been found that by using the circuits of the present invention, as herein described for instance, it is not, necessary to include the socalled double line frequency preparatory impulses nor is it necessary to slot the vertical synchronizing impulse at double line frequency. In

. the absence of such slotting and in the absence of the double line preparatory impulses the horizontal deflection generator may momentarily lose synchronism, however, synchronous operation of the horizontal oscillator will be resumed almost immediately following the vertical synchronizing impulse period. Furthermore, it has been found that adequate interlaced scanning at both the transmitter and the receiver may be accomplished even in the absence of the use of the double line frequency impulses and in the absence of the slotted vertical synchronizing impulses.

It is therefore one purpose of the present invention to provide a new, improved and simpliber of tubes and circuit elements and which will produce a picturefand synchronizing signal series which is entirely efiective to maintain synchronous operation of all receivers tuned to the transmitting station.

Another purpose or the present invention resides in the provision of a simplified system for producing the necessary picture signal series blanking impulses and the necessary horizontal and vertical synchronizing impulses that are transmitted during the blanking period.

Still another purpose of the present invention resides in the provision of means for simultaneously generating deflection voltage variations which may be used to directly cause deflection of the scanning cathode ray beam in the television transmitting tube or which may be used to drive a power tube for deflecting the scanning cathode ray beam.

Still a further purpose of the present invention resides in the provision of a circuit for generating voltage variations which may be used to deflect a cathode ray beam in a monitoring oscilloscope.

Another purpose of the present invention resides in the provision of a circuit for generating voltage variations of saw-tooth wave form that may be used to control devices for producing shading control signals.

A still further purpose of the present invention resides in the provision of a circuit arrangement which will produce the above referred to voltage variations in response to the application of properly tinied'horizontal and vertical synchronizing impulses.

A still further purpose of the present invention resides in the provision of a circuit arrangement for producing a desired composite picture and synchronizing signa1 series which may be used directly to modulate a radio frequency oscillator in order that the composite signal may be transmitted to a remote receiving station.

Still other purposes and advantages of the present invention will become more apparent to those 3 skilled in the art from the following specification and drawings wherein the single figure represents a preferred form of the present invention. Furthermore, the figure also shows various curves of voltage variations appearing at various parts of .the circuit.

For controlling the apparatus and circuit arrangement shown in the single figure and described in the following specification; a source of.

horizontal and vertical synchronizing impulses must be provided. Such a source is not shown in the drawing and it is to be, understood that the horizontal and vertical synchronizing impulses may be derived from any appropriate generator.

It is only necessary that the horizontal and vertical synchronizing impulses be of the desired frequency and be spaced with respect to each other by the desired amount. By way of example, a generator for supplying such impulses is shown and described in Schade Patent No. 2,254,626, issued on Sept 2, 1941.

Referring now to the drawing, the picture signals which'are derived from a television transmitting tube are applied to terminals Ill and ii, the latter of which is connected to ground. These signals may be derived from any desired television transmitting tube. The horizontal synchronizing impulses from any appropriate source may be applied to the terminal l2 while the vertical synchronizing impulses are applied to the terminal l4. I

The system includesdischarge tube I8, which in turn includes cathodes I8, two control electrodes 20 and 22, and two anodes 24 and 26.- These'elements may be enclosed in a single tube multi-vibrator and the operation of the multivibrator is synchronized by means of horizontal impulses which are applied to the terminal I2 from any desired appropriate source. The impulses which are impressed upon the input terminal I2 are applied to the control electrode 20 through coupling condenser 28. The control electrode 20 is connected to ground by way of the usual grid resistor 30 and in' order that the control electrode may be operated at aproper potential with respect to cathode I8 a resistance 32 is also included "between the control electrode and terminal 34 to which a positive potential is applied. The positive supply potential that is applied to terminal 34 is tie-coupled from the elements of tube l6 by de-coupling resistance 36 and condenser 38., The anodes 24 and 26 are also connected to the positive terminal 84 by way of anode load resistance 40 and 42, respectively. The anode 24 is coupled to the control electrode 22 by means of coupling condenser 44 while the control electrode 22 is connected to the cathodes l8 by means of resistance 46 and potentiometer 48. One end of the resistance element of the potentiometer 48 is connected to the resistance 48 whereas the other end of the resistance element of the potentiometer, as well as the movable contact thereof, are connected to the cathodes IS. The anode 28 is connected to output terminal 50 and to ground through condenser-B2. while the control electrode 22 is connected to output ter- .minal. 64 by way of resistance 58. The resistance 58 has connected in parallel therewith a-condenser 58. The cathodes 3 are connected to ground by way of variable resistance 85 and in-- .4 purpose of providing the inductance in the oathode circuit of tube i6 is to provide an inductive feedback impedance in order that short impulses of high amplitude may be produced. The widths of the produced impulses may be readily controlled by varying the amount ofthe resistance 6| which controls the cathode impedance. The speed ofoperation of the multir-vibrator which includes the elements of tube 16 may be controlled by adjusting the potentiometer 4B.

When horizontal synchronizing impulses are applied to the terminal l2 with the impulses extending in a negative direction, electronic current from cathode 18 to anode 24 is reduced durin application of the individual impulses. This reduction in anodic current causes positive 1111-- pulses to appear at the anode of tube 24 and these impulses are applied to the control electrode 22 of tube i6 through condenser 44. The heavy cathode current that is caused to flow drives the cathodes in a positive direction causing the current to anode 24 to be completely cut-oil and since the anode 24 is connected to terminal $9, the strong impulses produced at anode 24 are then available at. terminal 60 and may have a wave form such as that represented by the curve 65. Naturally the impulses extend in a positive direction and occur at a frequencycorresponding to the synchronizing impulses applied to the control electrode 20 but of a time duration (or width) determined by the resistance 6|.

The circuit also provides a\source of deflection voltage variations which may be derived from terminal 54 and which may have a wave form similar to that shown by curve 64. These impulses are derived from the control grid 22 and the parallel resistance and condenser combina tion 56-58 are included between the control elec.

' trode 22 and the terminal 54 in order to produce wave shaping (and biasing of the following tube) to provide the desired voltage variation or wave form. It will be noticed that this wave form is substantially that necessary for driving a power tube for supplying horizontal deflection voltages for deflecting the scanning cathode ray beam in an Iconoscope or s1milar television transmitting tube where electromagnetic deflection is used.

When condenser 52 is'connected between the anode 26 and ground, the triode section including anode 26 of'tube it operates as a discharge tube as well as a part of the multi-vibrator with the result that voltage variations of substantially sawtooth wave form may be obtained from the anode 26. As stated above, these voltage variaations are available at terminal 50 and may have, a wave form corresponding to the curve shown at 86. In so far as this part of the operation is con-. cerned, the condenser 52 charges through load resistance 42 and decoupling resistance 38 and is discharged by current flow between cathode i8 and anode 28.

From the above it may be seen, therefore, that the single tube i6, together with its associated circuit elements, operates both as a multi=vibrator and as a discharge tube for producing several sources of voltage variation. From the terminal 60 may bederived horizontal blanking in 1-- pulses of a width determined by the resistance 8i while from the terminal may be derived volte variations of a wave form such asare suitable for driving a horizontal deflection power tube. Furthermore, the sawtooth wave form voltage variation which are derived from terminal 5&3 maybe conveniently used for horizontally deflecting the cathode ray beam in an oscilloscope'tube, particularly where the cathode ray beam of the oscilloscope is electrostatically deflected. This voltage, as stated above, may also be used to con trol a shading signal generating device.

A somewhat similar circuit arrangement is also provided for producing similar voltage variations at vertical deflection frequency. This circuit a1- rangement includes tube 68 which in turn includes cathodes I0, control electrodes 12 and '14 as well as anodes l6 and I8. The elements of the tube 68 are connected as a multi-vibrator and the operation of the multl-vibfator is synchronized by vertical synchronizing signal applied to the terminal I4. Resistances 8d, 82 and 84 are connected in series and the series arrangement is connected from input terminal I4 to ground. The control electrode 12 is connected to the lunction of resistance 82 and 84 by means of series connected resistance 86 and condenser 80. Furthermore, a condenser 90 i connected between the control electrode-I2 and ground. The inclusion of the resistance 86 and the condenser so provides a time delay circuit in order that the vertical synchronizing impulses which are applied to the terminal I4 will be delayed by a predeterm'inedamount before being applied to the control electrode 12. The anode I0 is connected to terminal 34, to which is applied a positive potential,

by means of load resistance 02, potentiometer 94 and de-coupling resistance 96. A de-coupling condenser 93 is connected between the junction of potentiometer 94 and de-eoupling resistance 98 while the movable contact of the potentiometer 04 is also connected to the junction of the potentiometer and the de-coupling resistance 96. The

anode 8 is also connected to' the de-coupling resistance by means of potentiometer I00. The cathodes I0 are connected to ground by way of cathode resistance I02, the resistance being bypassed by condenser I04 in order to round oil. the front edge of the feedback, impulse. This action,'in so far as the feedback is concerned, effective to prevent unstable triggering oi the circult and greatly increases the stability of interlace. Voltage variations which are present at the anode iii are applied to the control electrode 14 by way of coupling condenser I04 while the control electrode .'4 i connected to ground by way of resistance I06 and potentiometer I08. 'Ihe potentiometer I08 is connected as a variable resistance and is eflective to control the free operating speed of the multiibrator.

The vertical synchronizing impulses which are also connected to ground by ausual grid resistance H6. The cathode of tube H0 is connected to ground by cathode resistance 8 while the anode of the tube is connected to the positive terminal 3- by means of anode load resistance .2

When vertical synchronizing impulse signals are applied to the control electrode I2 of the. multi-viorator tube v68 aiter a predetermined time. delay, the operation of the mum-vibrator is controlled and synchronized with the vertical synchronizing impulses tions which extend in a positive direction. These voltage variations are present on conductor I22 and are applied to a further delay circuit including resistances I24 and I20 as well as condensers I28 and I30. The combination of resistance I24 and condenser I28 as well as the combination of resistance I26 and condenser I30 provide a further time delay for the voltage variations present at anode I6 andthese delayed voltage variations are then available at conductor I32. The wave form of the delayed voltage variations may have a wave form similar tothat shown a curve I84. The anode of tube Il0is connected to conductor I32 by means of resistance E36 and since the voltage variations appearing at the anode of tube I I0 are not delayed, these voltage variations when combined with the delayed voltage variations from the anode of tube 16 produce a vertical blanking impulse such as shown at curve I38 the duration of which is sufllcient to provide the necessary vertical blanking.

Furthermore, the multi-vibrator including tube 68 and its associated circuit elements also pro-, duces voltage variations which are available at the control electrode I4 and which are applied to terminal I40, these voltage variations being similar to those shown by curve I42 and suitable for energizing a vertical deflection power tube. These voltage variations are therefore similar to thewoltage variations which are available at terininal 54 and may be ultimately used'in deflect-. ing the cathode ray beam in the television transmitting tube. particularly where the beam is deflected by electromagnetic means as is the case in an Iconoscope. Connected between anode 18 and ground is a condenser I44 and this condenser is charged through anode load resistance I00 and de-coupling resistance 00. The condenser I44 is discharged by that portion of tube 68 including anode I8 to operate as a sawtooth. wave generator so that voltage variations of sawtooth wave form may be derived from the anode 18. Actually, these voltage variations are available from the movable contact of potentiometer I00 and are applied to terminal I48. They may have a wave form such as that shown by curve I48; As explained above, these voltage variations of sawtooth wave form maybe conveniently used for deflecting the cathode ray beam In an oscilloscope particularly where electrostatic deflection is used. The voltage variations may be used directly orafter appropriate amplification. They may also be used to control vertical shading tubes.

From the circuit as so far described, it may be seen that a very simple and convenient circuit arrangement has been provided for generating horizontal and ver ticei blanking impuiues and for simultaneously generating horizontal and vertical deflection driving voltage variations. These deflection driving voltage variations, after appropriate amplification, may be used to deflect the cathode ray beam in the television-transmitting tube. Furthermore, the circuit arrangement also provides a .source of voltage variations of sawtooth wave form and of horizontal and vertical frequency which may be conveniently used for deflecting the cathode ray beam in the monitor-- ing oscilloscope.

As' stated above, the picture signals as' derived from the television transmitting tube are applied to terminals I0 and II. signals must be suppressed at various regularly spaced intervalsin order that the suppressed and the circuit operates to produce at the-anode I8 delayed voltage varia- These picture blanking control impulses.

' signal blanking tubewhereas tube I52 is the synchronizing signal insertion tube. Both tubes when supplied with proper voltage variations operate to produce the final composite picture and synchronizing signal series.

Tube I54 includes cathodes I56, control electrodes I58 and I66 as well as anodes I62 and I64- The cathodes I56 are connected to ground while the control electrodes I58 and I66 are connected to ground by way of grid resistors I66 and I68, respectively. The anode I62 and I66 are connected to the positive terminal 34 by load variations extending in a positive direction to cause modulation of anodic current in tube I54. Since the blanking impulse extend in a positive direction, the voltage variations at the in that tube.

anodes I62 and I64 will extend in a negative direction upon the application of the blanking impulses to the control electrodes I58 and I60.

The anode I62 is connected to the anode I64 by means of a tuned circuit includinginductance I18 and capacitance I86, this combination being connected in series with condenser I82.- The purpose of the inductance I18 in the condenser I86 is to improve the wave former the horizontal If desired, these elements may actually be omitted, in which case the anodes I62 and I64 are directly connected together and a single common load resistance I72 is used. The voltage variations from the anodes I62 and I64 are combined and are applied to the suppressor grid or electrode of tube I56 by way of coupling condenser I84. The wave form of the combined blanking control impulse may be similar to that shown at I86. The screen'grid of tube I50 is connected to positive terminal 34 by way of resistance I88 and potentiometer I86. The resistance element of the potentiometer I96 is connected between positive terminal and ground whereas the movable contact of the potentiometer is connected to the screen grid resistor I88. The screen grid is decoupled for relatively rapid voltage variations by means of condenser I62. The cathode of tube I50 is connected to ground by an unbypassed cathode resistance I84, particularly if good white signals are available and ii the television transmitting (camera) tube is operated at normal gamma. Under low light conditions, and where a transmitting tube similar to an-Iconoscope is used, a bypass condenser may be used to prevent by means of an appropriate load circuit which will be explained later. The suppressor electrode 'of tube. I46 i maintained at a predetermined positive potential with respect. to ground by means of voltage divider resistances I98 and 666. The Junction of voltage divider resistance I68 and 200 is connected to the suppressor electrode by means of a further resistance 262.

When picture signals are applied to the control electrode oi. tube I50 by way of condenser 264 they operate to modulate the electron stream The picture signals as applied to terminals I6 are polarized such that blackin the picture is represented by a, change in the negative direction whereas white in the picture is represented by a voltage change in the positive direction. Accordingly, when signals representing black are applied to the control electrode of tube I56, the voltage variations at the anode of that tube will extend in a positive direction. In order to afford the desired blanking at horizontal and vertical deflection frequency, the voltage variations which are applied to the suppressor electrode by way of condenser I84 from anodes I62 and I66 of tube I54 are effective to cut-off the current flow through tube I50. As stated before, the voltage variations from the anodes I62 and I66 extend in a negative direction and are suificiently intense to reduce the anode current in tube I56 to zero. Accordingly, during such blanking intervals, applied picture signals are ineffective to produce any potential change at the anode of tube I50 which is driven to its most positive potential. The height of the blanking pedestal or, in other words, the potential change of theanode of tube I56 during blanking intervals may be controlled and determined by the position of the movable contact on potentiometer I96 which controls the energizing .potential in the screen grid electrode of tube I50. The signal at the outputof tube I56 therefore represents the picture signals applied to terminal I6 with certain inter-- spond to blacker than black in so far as their intensity is concerned. The synchronizing signals are not delayed with respect to the front edge of the blanking impulse as is the practice in some synchronizing systems since it has been found that the front edge of the synchronizing impulse and the front edge of the blanking impulse may coincide without producing any undesired results.

Tube I52 includes a cathode, a control electrode, a screen grid electrode, a suppressor electrode and an anode. The cathode oi the tube is connected directly to ground whereas the control electrode is connected to ground by resistance 268 in parallel with which is connected a condenser 268. The suppressor electrode is also connected to ground by resistance H6 and is coupled to a suppressor electrode of. tube I56 by way of coupling condenser 2I2. The horizontal synchronizing signals are then applied to the suppressor electrode of tube I52 from the blanking tube I54but in this connection is included condenser 2I2 and resistance 2I6. These elements perform adifferentiating' action to differentiate the horizontal blanking impulse to thereby produce a shorter horizontal synchronizing impulse. There therefore, appears on the suppressor electrode of tube I52 the horizontal synchrcninng impulse which is in fact the dinerentiated hdlf'i tical synchronizing impulses to the control electrode of tube I52.

Since the horizontal synchronizing impulses that are applied to the screen grid electrode I52 and the vertical synchronizing impulses that are applied to the control electrode of tube I52 extend in a negative direction, these impulses operate to reduce the current flow through tube '52 with the result that the anode is driven in a positive direction during such intervals. a

The screen grid of tube I52 is connected to the movable contact of a potentiometer 2I8. One

end of the resistance element of the potentiomete 2|8 is connected to ground whereas the other end of the resistance element is connected to the positive terminal 34 by way of resistance 220. This permits the application of a predetermined relatively small positive potential to the screen grid electrode, the electrode being bj-passed to ground in so far as alternating current potentials are concerned by condenser 222. An ad- :lustment of the value or the potential applied to the screen grid electrode which is made possible by an adjustment oi potentiometer 2I8 determines the height or intensity of the synchronizing signal impulses appearing at the anode of tube I52.

The anodes of the blanking tube I50 and. thesynchronizing signal insertion tube I52 are connected together and are in tum connected to positive terminal 34 through series connected inductance 224, a further inductance 226, a resistance 228 and a de-ooupiing resistance 230. A de-coupling condenser 232 is connected between ground and the junction of resistance 228 and 230 in order to stabilize the voltage applied to the anode load circuit of tubes I50 and I52. An output circuit is provided between ground and the synchronizing impulses are present and accord- I ingly no horizontal synchronizing signals are transmitted during the transmission of the vertical synchronizing signals. The inclusion of the inductances 224 and 226 prevents a loss of the high frequency components of the signal series. Preferably tubes I50 and I52 should be of the high gain type such as, for example, tubes 6A6"? (1852) for example. Such a tube having a screen electrode between the suppressor electrodeand the anode may also be used advantageously.

There therefore appears at the output terminals 236 a composite wave form including picture signals and interspersed blanking and synchronizing signals. Such a wave form after desired amplification may be used directly to amplitude or frequency modulate a radio frequency carrier wave in order that th signals may be transmitted.

The circuit shown in the drawing and described above is particularly adapted for portable television equipment and provides the necessary voltage variations for operating such equipment. The principal elements necessary in addition to the circuit described are naturally a source of pictur signal, a source of horizontal and vertical synchronizing impulses and a source of radio frequency energy particularly where radio transmission is desired. With these additional elements it is possible to transmit t levision images and to, in addition, monitor such transmission a by means of the usual cathode ray oscilloscope.

The horizontal and vertical synchronizing impulses which are applied to terminals l2 and I4 may be derived from any desired suitable source or, in fact, these signals may be supplied from the main television transmitter so that they are properly related to the 60 cycle power supply line.

' The horizontal and vertical synchronizing imjunction of inductances 224 and 223 through condenser 234 so that the output energy is available flOi'Il terminals 235. The inductance 224 is paralleled by a resistance 238 in order to slightly modify the wave form at the output terminals.

It may be seen therefore that picture signals when applied to the con rol electrode of tube I cause a corresponding voltage drop in load resistance 228 to produce amplified voltage variations at the output terminal 236. The horizontal and vertical blanking impulses which are appl ed to the screen grid electrode of tube I50 reduce the currentiiow through that tube to zero, with the result that the potential at the output terminal 235 is altered in a positive direction. The plate current of the parallel synchronizing insertion tube I52 also causes a voltage drop in the com 'mon load circuit resistance 228. The plate curpulses may be transmitted to the portable equipment from the mair transmitter by the use of a separate carrie for that purpose or such signals may be separated from the television signal trans mitted ijrom th principal transmitting station.

The picture signals may be derived from any television transmitting tube such as, for example, an Iconoscopef an "Orthicon or a fMonoscope.

Since the monitoring oscilloscope is generally relatively small and it has a screen of about 3 inches in diameter, the electron beam in such a tube is normally electrostatically deflected and, accordingly, the voltage variations of sawtooth wave form which are available at. terminals 50 and I46 may be conveniently used for horizontally and vertically deflecting the cathode ray beam in the monitor tune. If it is desired to observe only the signal trace in the monitor tube then the-h0fiZQIltfl1 deflection of acathode ray beam therein may be produced by either the horizontal or vertical deflection voltage while the vertical deflection oi the cathode ray beam may b produced as a function of energy derived from the output terminals 236.

From the above it may be seen that 9, relatively compact and simplified synchronizing signal generator has been provided which operates to pro duce not only the desired blanking and synchronizing impulses but also produces voltage variations which may be used to deflect the cathode ray beam in the television transmitting tube. Furthermore, the same system provides means for generating voltage variations of sawtooth wave form in order that a monitoring cathode ray tube may be used at the portable transmitter.

Y 11 The system described also operates to blank the picture signal series at predetermined intervals and to superimpose upon the blanking signals the desired synchronizing signals in order that a complete composite series of picture and synchronizing signals may be produced.

The vertical 'synchronizing impulses may be of any desired length but it is preferable if their length is chosen to equal approximately one line deflection duration as shown by the curve applied to the output terminals 236 in order to reduce the possibility Of the horizontal deflection generator in the receiver from momentarily dropping out of synchronism. Vertical synchronizing signals persisting for only one-half a line may even b .used without resulting in any difllculty in segregating the horizontal and vertical synchronizin signals.

Although the system is described in more or less detailed form it is to be understood that various alterations and modifications may be made therein and any and all such modifications are to be considered within the purview of the present invention except as limited by the hereinafter appended claims.

I claim:

1. A television transmitting system including a source of picture signals, a picture signal blanking tube including a cathode, a pair of. control electrodes and an output electrode, a synchronizing signal insertion tube including a cathode, a

.pair of control electrodes and an output electrode,

means including a common load circuit for maintaining the output electrodes positive with respect to their associated cathodes, means for applying picture signals to one control electrode of the picture signal blanking tube, means for applying horizontal and vertical blanking signals to the other control electrode of the picture signal blanking tube, means for applying vertical synchronizing signals to one control electrode of the synchronizing signal insertion tube, and means for applying horizontal synchronizing signals to the other control electrode of the synchronizing signal insertion tube, whereby a composite series '01, picture, blanking and synchronizing impulses may be derived from the common load circuit of the tubes.

2. A television transmitting system wherein picturesignals are available, comprising a picture signal blanking tube including a cathode, a pair of control electrodes and an anode, a synchronizing signal insertion tube including a cathode, a-pair of control electrodes and an anode, means including a common load impedance for maintaining the anodes positive with respect to their associated cathodes, means for applying picture signals to one control electrode of the pic ture signal blanking tube with signals representative of black in the picture extending in a negative direction, means for applying horizontal and vertical blanking signals 01' predetermined diilerent frequencies to the other control electrode 12 3. A television transmitting system including a source of picture signals, a picture signal blanking tube including a cathode, a first and'second control electrode and an anode, a synchronizing signal insertion tube including a cathode, a first and second control electrode and an anode, means signals of one frequency to the first control elecof the picture signalblanking tube with the ,blanking signals extending in a negative direction, means for applying vertical synchronizing signals to one control electrode of the synchronizing signal insertion tube, and means for applying trode of the synchronizing signal insertion tube, and means for applying synchronizing signals of another frequency to the second control electrode of the synchronizing signal insertion tube, whereby a composite series of picture, blanking and synchronizing signals may be derived from the common load impedance of said tubes.

4. A television transmitting system wherein a source of picture signals are available, comprising a picture signal blanking tube including a cathode, a first and second control electrode and an anode, a synchronizing signal insertion tube including a cathode, a first and second control .electrode and an anode, means including a common anode load circuit for maintaining the anodes positive with respect to their associated cathodes, means for applying picture signals to the first control electrode of said picture signal blanking tube, means for applying picture signal blanking voltage variations of a predetermined wave form to the second electrode of said picture signal blanking tube, said voltage variations extending in a negative direction, whereby intermittent portions of the picture signal series will be suppressed and whereby anodic current in said picture signalblanking tube will be eliminated during periods of suppression of the picture signals, means for applying synchronizing signals of one frequency .to the first control elec- 1 trode of the synchronizing signal insertion tube, and means for applying synchronizing signals of another frequency to the second control electrode of the synchronizing signal insertion tube, the synchronizing signals extending in a negative direction, whereby a composite series of picture, blanking and synchronizing signals may be derived from the common load circuit of said tubes- 5. A television transmitting system including a source of picture signals, a picture signal amplifying tube including a cathode, a control electrode and an anode, a synchronizing signal insertion tube including a cathode, a pair of control electrodes and an anode, means including a common load circuit .for maintaining the anodes positive with respect to their associated cathodes, means for applying picture signals to the control electrode of the picture signal amplifying tube, and means for applying horizontal and vertical synchronizing signals individually to the pair of controlelectrodes in said synchronizing signal insertion tube, whereby a composite series of picture and synchronizing signals may be derived from the common load circuit.

ing a picture signal amplifying tube including a cathode, a control electrode and an anode, a synchronizing signal insertion tube including a cathode, a pair of control electrodes and an anode, means including a common load circuit for maintaining the anodes positive with respect to their associated cathodes, means for applying picture signals to the control electrode of the picture signal amplifying tube with the signals representing black in the picture extending in a negative direction, and means for individually applying horizontal and vertical synchronizing signals to the pair of control electrodes in said synchroniflng signal insertion tube with the synchronizing signals extending in a negative direction, whereby a composite series of picture and synchronizing signals may be derived from the common load circuit.

7. A television transmitting system including a source oil picture signals, a picture signal blanking tube including a cathode, a pair of control electrodes, a screen grid electrode, and an anode,-

a synchronizing signal insertion tube including a cathode, a pair of control electrodes, a screen grid electrode and an anode, means including a common load circuit for maintaining the anodes positive with respect to their associated cathodes, means for applying picture signals to one of the control electrodes of the picture signal blanking tube, means for applying horizontal and vertical blanking impulses to the other control electrode of the picture signal blanking tube, means for applying vertical synchronizing impulses to one of the control electrodes of the synchronizing signal insertion tube, means for applying horizontal synchronizing impulses to the other control electrode of the synchronizing signal insertion tube, means for applying an adjustable positive potential to the screen grid electrode of the picture signal blanking tube in order to control the intensity of the produced blanking pedestal, and means for applying an adjustable positive potential to the screen grid electrode of the synchronizing signal insertion tube in order to control the intensity of the produced synchronizing signals, whereby a composite series of picture, blanking and synchronizing signals may be derived iromthe common load circuit of the tubes.

8. A television transmitting system including a source of picture signals, a picture signal blanking tube including a cathode, a pair oi control electrodes, a. screen grid electrode and an anode, means including a load circuit for maintaining 'the anode positive with respect to its associated cathode, means for applying picture signals to one 01' the control electrodes of said tube, means for applying horizontal and vertical blanking impulses to the other control electrode or said tube, and means for applying an adjustable positive potential tothe screen grid electrode of the picture signal blanking tube in order to control.

theintenslty of the produced blanking pedestal, whereby a composite series 01' picture and blanking signals may be derived from the load circuit or said tube.

9. A television transmitting system including-a source of picture signals, a picture signal amplitying tube including a cathode, a control electrode and an mode. a synchronizing signal insertion tube including a cathode, a pair oicon-1 trol electrodes, a screen grid electrode and an anode, means including a common load circuit for maintaining the anodes positive with respect to their associated cathodes. means for applyins 14 picture signals to the control electrode of the picture signal amplifying tube, means for applying vertical synchronizing impulses to one of the control electrodes of the synchronizing signal insertion tube, means for applying horizontal synchronizing impulses to the other control electrode of the synchronizing signal insertion tube, and means for applying an adjustable pos itive potential to the screen grid electrode oi the synchronizing signal insertion tube in order to control the height of the produced synchronizing signals whereby a composite series of picture and synchronizing signals may be the common load circuit of said tub 10. A television transmitting system wherein picture signals and vertical synchronizing impulses are individually available comprising a picture signal blanking tube including a cathode. a pair of control electrodes and an anode, a synchronizing signal insertion tube including a cathode, a pair of control electrodes and an anode, 7

means including a common load circuit for maintaining the anodes of the picture signal blanking tube and the synchronizing signal insertion tube positive with respect to their associated cathodes, means for applying picture signals to one of the control electrodes of the picture signal blanking tube, means for applying combined horizontal and vertical blanking impulses to the other con trol electrode of the picturesignal blanking tube, means for applying the vertical synchronizing impulses to one oi the control electrodes of the synchronizing signal insertion tube, and means for applying diii'erentiated blanking signals to the other control electrode of the synchronizing signal insertion tube, whereby a composite series oi picture, blanking and synchronizing impulses may be derived from the common load circuit of the tubes. v

ii. A television transmitting system wherein picture signals and vertical synchronizing impulses are individually available and wherein a source of combined horizontal and vertical blanking impulses is provided, comprising a picture signal blanking tube including a cathode, a pair of control electrodes 'and an anode, a synchronizing signal insertion tube including a cathode, a

' pair of control electrodes and an. anode, means including a common load circultior maintaining the anodes oi thepicture signal blanking tube and the synchronizing, signal insertion tube positive withrespect to their associated cathodes.

means for applying picture signals to one or thecontrol electrodes of the picture signal blanking tube with signals representing black in the picture extending in a negative direction, means for applying the combined horizontal and vertical blanking impulses to the other control electrode of the picture signal blanking tube with the impulses extending in a negative direction, means for applying the vertical synchronizing impulses to-one. of the control electrodes of the synchronizing signal insertion tube. and means for applying diflerentiated blanking signals to the other control electrode oi the synchronizing signal ino'r'ron. comma derived from 

